Emile placet and joseph bonnet



, invention.- By our processes, as hereinafter these processes we usesalts and oompou ads invented new and usefulImproveme'nts in theplicable to metals which are very (liflicult to obtain by electrolyticaction, such for examchromium'which, so far as'we are aware, has

miumcf great purity, in coherent masses of suflic ent size foryariousindustrial uses,and

UNITED: STATES PATENT OFFICE.

EMILE PLAGET AND JOSEPH BONNET, OF PARIS, FRANCE.

PROCESS OF ELECTRODEPOSITION'OF C'HR OMIUM.

SPECIFICATION forming part of Letters PatentNo. 526.114, dated September18, 1894.

Application filed August 20,1892. Serial No. 443,640. N p

091161150 Patented in France November 12, 1890, No. 209,469,

and July 17, 1891, bios. 214,940,214341, 214,942, and 214,943; inBelgium November 18,, 1890, No. 92,775 in England November 27, 1890, No.19,344, and December 81, 1891., No. 22,856; in Sweden November 29, 1990,No. 4,267: in, Norway December 4, 1890, No. 2,283; in Germany December5, 1890, No. 66,099i in Spain March 3, 1891,110. 11.587. and in'Austria-Hungary March 24, 1891, No. 53,381 and No- 8,074.

To all whom it may concern.-

Be it known-that we, EMILE PLACET and JOSEPH BONNET, citizens of theRepublic of France, and residents of Paris, France, have Electrolysisof- Chromium, of which the following specification is a full, clear, andexact description.

The said improvements havebeen, wholly or in part, patented to us in thefollowingn'a'med countries: France, dated November 12, 1890, No.209,459, and-July 17,-1891, Nos. 214,940, 214,941, 214,942, and 214,943;Belgium, ,dated November 18, 1890, No. 92,775; England, dated November.27, '1890, No.

Germany,dated December 5, 1890,.No. 66,099 5 53,381 and No. 8,074;Spain, dated March 3, 1891, No. 11,537; Sweden, dated November 29,1890,No. 4,257, and Norway, dated December 4,1890, No. 2,283.

In aformer applicatiom'filed December 10, 1890, Serial No. 374,184, wehave described a general electrolytic process particularly appleas ironand chromium. The present invention, whileapplicable to other metals,relatesmore particularly to the electrolysisof' not been obtained inthis manner prior to our set forth, we obtain elec'tro-depo'sit'edchroof' dilferent colors, as may be desired. In

ot'chromium which, heretofore have never been used or proposed fior'usetor. the pur-' pose in view,"and from which, in the manner hereinafterpointed out, metallic chromiumis produced in sufficient quantity, andwith sufficient economy to constitute an industrial. process, verydifierent from theresult of laboratory experiments by which theproduction of minute specimens of metallic chromiu m has been heretoforeattempted. 1

In'the following detailed description we. have given the salts orcompounds from which metallic chromium can be obtained commercially,specifying the proportions and compositions of the baths, and indicatingthe variations desirable with different compounds. The most important ofthese compounds is chromic acid, either the commercial acid,-or

chromic acid obtained from chromate or biohromate of an alkali metal.The method of using chromic acid isdescribed under paragraph first,below.

' In-paragraphs second to eleventh, we have described the employment ofa series of chromic compounds, as sulphate of chromium, chrome-alum,orother salt of the sesqui-oxide of chromium,azotate of chromium, andother compounds which are equivalents for the purposes of the invention,and in connection with all of which we employ an alkaline sulphate oralkaline earth-metal to increase the deposition. Finally underparagraphs thirteenth and fourteenth .we describe the procedure whenheat'is employed.

We willnow describe in detail the principal baths; which we haveactuallyused. and from which the results referred to have been obtained.

First. A solution of chromicacid in water. This solutionmay be verylittle concentrated. One to two grams of. chromic acid in one hun dredgrams of water-are sulficient. However, the more the solution isconcentrated, the more abundant is the deposition.' We vary the shade'ofthe metal deposited by addingtp U the solution a small quantity (forexample-- live to ten grams per liter) of one of the 01 lowing acids:The. phosphoric, sulphurous, 0x alic, benzoic, formic, gallic,pyrogallic, picric,-

phenic,-salicylic, and other 'analogousacids,

give very whitefdepositions of chromium. 1 I

The acetic, hydrQ-fluosili'cic, &c., acids-give brilliant deposits, butd'eeper. Boric acidgives dim grayish depositions, but very abundant.Einally sulphuric, azotic, chlorhydric, arsenious,-tartaric-, citric,lactic, tannic, &c.;

acids give depositions ofa, more or less deepshade, according to thequantity employed.

. 65 an alkaline snlpha'te or-alkaline eartbmetal,

To prepare our solution of chromic'alcid, we make use of-chromicacidobtained by the ord1i 1ary processes, or else, we produce chromic -3Cid1fl the bath itself, in proportion as the dep- 5 oslt-ion of chrominm'is'made. In this case we employ as a bath, a solution of'an alkal nebichromate, and we pour into this solu- Men, in small successivequantities, an acid (sulphuric acid, nitric acid, hydroflug-silicic, orany other acid) whichin combining'with the alkaline base, sets thechromic acid free, or else, we prepare the chromic acid by putting ansuspension oxide of chromium hydrated in i a soiutionof oxalic acid, orofi 'anyiotherorganlc acid, andpassing through it'a cur'rentofelectricity. ,At the end of a very'short'It-ime,-

. under theiniluence of the electricity, the oxide of chrominm isfoundtransformed into chromic ac1d, acco'rding'to the -forn1'ula,2(()r 02c 60 =;4(C r O The best results,,how.ever, are

obtained bynsing chromic acid produced by ,means of electricity in the{allowing-way: We. prepare, first; a solution of chromate or bichroniateof anlalkalimetal and insert'-- therein a porousyessei-containingthesame solution, or simply pure water, and contain-Jug-1 also an electrode of carbon, platinum, or other conductorwhichwili, not be attacked. In the external-solutionis placedaiiotliersuih 3o able' .electrode with which, is connected ther--.pos1tiv e pole Of'fll electric genegator. After.

the electric-genri'nt passedIor sometime all of the alkaliwiil'hayepassed into the poious vase, 'leaying chromic acid in solution-Lin 5 thevesselgcontaining.the-positwe electrodr d-nieeh mjicracidis absolutely,pine, and

su table not ohlyfon-the-fnrtheroperation of! -obt'ai ningchromium, butfor various indgset ,tr1 'a1 uses. We obtain directly by electrolysis 4omixtures or alloysof chromiumandoiidi iei ent metals, by dissolvinig,inour baths oi." chrom c acid, oxides or carbonates-which do notdecompose the fchromicacid; such as the oxides or the carbonates ofccppen ofiron, of alnmmlum, of magnesium, of tnngsten, 10fmolybdennmfof; nickeh-ofjsiilfver, 65c YWe also obtainelectrolytic-deposits o'ficlirominm by employingtlie following baths:,fSecond. A solution of ten, fifteen ort-wenty v gramsof sulphate ofchromium in c'ne'hnn- 3 I dred grams of' yvater. We addto this seinlionsulphuric acid until no more oxidefof hr mium is deposited at thenegative; poles When the deposit of oxide ceases it will: be known thatthe'bath is snflici'entlyzacidu Third. Instead ofsnlphate of chromium-weemploy by preference, chrome alninxd'oubie sulphate'ofch'romiu m-and ofpotash, of soda 6o or of ammonia); hecausfefthe chrome-alumis moreeasytopreparer Weiacidnlate it'li kewise by means of sulphuric acid. Tomain. tate the %deposi tion,1;ve find it advantageous to add to ourbaths,'t en to fifteeri'per cent. of

or of afmixtnre of them.

late our baths, we may also employ azomc, phosphoric, chlorh'yd'ric,hydroflnosilicic acids; and the organic acids, or a mixture of theseacids. It is thus'we have composed the following bath: tento fifteengrams chrome alum; ten to fifteen grams sulphate of pot--,

ash of soda or of ammonia; five grams oxalic. -aci or other organicacid; and one hundred 7 5 grams of water. We heat-this solution, whichis green, until it becomes violet; and we obtain a bath which gives,magnificent deposi- "tions ofehromium.

Fitth. .We dispense with acidniating our 8o baths, by employing fortheir :i'oundation; salts very acid" by themselves, .sucli'as'thebisuiphate's, the bihospiiates, the iii-acetates, d e; The acid vi ichis found: combined in these salts in definite; proportions, acts (forthe end we propose) in muc better condie1 'tions than whenwe add the id'directly to the bath} We name for gamm mmen to; twenty gramsot'chrom'e-alnm, 'fiyeto' te'n grams of neutral-or alkalinesnlpha-te,'fi1ire to" p A tengramsof alkaline bi-sulphate, and one 4hundred grams of Water. "T l Sixth, To a solution'ofl chrouiic' mayorchromate or bi-chromate of an alkali mf etaip we adda small quantity ofany acid(s'ni' hur'ic '95 acid, chlonhydri'c,"phosphoricfot other." eadd,;further, a sulphate, a chloride-Cor other alkaline salt; and weobtain a batlkwhioh-is' very' easily redncibleby electricity. We-takeg lfor ex'am'ple-teh to fifteen grams of 11-;81kfl'1 VIC-Ciliue"bi-chroinate, five to com grain s qf-:any-- slit-table acid,fifteen; to tw nt grains of chime-slan ed one hundred gramsof 'wafl f simes? i t e aiehoi or", I fany other-reducin bodpm rg u m g jtion. morerapid. 2 v

Seventh: In a solution of chrome-alum, or any other salt of'sesquioxide'fofl; ch rp'mium,

iwepour a soiutjio'irbf an alkaline-.bbcarben- I v ate and obtain aviolet precipitate; In plnngno-1' "ing'into theliquoxgwhich holds in'suspen-- sion this violet precipitate, the t'woelectrodes "of a batteuysye obtain depositiondf ch'rominm attheTnegative pole,

Eighth. we may add to surf-baths Dom: i5,

.tion OLsodd-Or 'of potash get cyanide's or of alkaline'snlpho-cyanides,holdingiin solution gor. in suspension oxide ofichromin'm drjcyanide ofchromium.

Ninth. :Inineaiq r 11ibin-nmilfi[fine can; :m "above, we sometimesflnddtndvantageous to employ-thesalts of chrqmidi sing aisn'it':TefithfTh roeeo-chro nie salts Qor will mama-techs an, exa ple; an the"most:-

simple-bf thesebath's; Wetak ehydrate' ot; sesqniokideofivioietchrome,and we'dis'solve otheramlnoniacai salt.) Under the influence 1 Foprfll;Insteadof sulphuric acidto tent;

Cf electricity this, bath gives at the'neg-a tiy e pole a magnificentdeposit of chromium. In-

adding to this bath an acid (chlorhydrie acid, or sulphuric acid,azotic, &c,) a series of chrome underthe influence of an electriccurrent. p a t Eleventh. Instead of alkaline sulphatesas we haveindicated above-as an example, to facilitate the deposition ofchromium-we employ likewisethe alkaline nitrates, phosphates,pyrophosphates, fluorides, fiuosilicates, borates, chlorides, chlorates,sulphurets, benzoates. oxalates, tartrates, citrates,

. ally be mixed with each other, and the recovacetates, sulphites,bi-sulphites, & c., or alkaline earths. For example:fi'fteen to twentygrams of chrome-alum or of-fluosilicate of chromium, ten to fifteengrams of fluosilicate of potash of'soda or of ammonia, five to ten gramsof hydrofluosilicic acid. or any other suitable acid,and one hundredgrams of water. We maintain the composition constant in our baths,either by means of a soluble anode, or by theaddition of oxide ofchromium, or of salts similar to those which compose these baths, or bymeans of a methodic circulation of solutions more or less concentrated.The baths that we havejustindicated may gener cry of the substanceswhich compose them may vary within very great limits, according to thequality of the metal it is desired to obtain. Small quantities ofalcohol, of gelatine, of sugar, of glycerine, or of other analo-' gousmatters, added to these baths produce a favorable action on the qualityof the metal deposited. These and analogous organic substances improvethe quality of the deposited metal, as shown by actual results. Thisaction may be due to a better grouping of the molecules, which is insome way favored by the presence of the above named substances. Theexplanation of the action is obscure,but the effect certain.

Twelfth. We obtain, directly by electrolysis, alloys of chromium ofvarious metals; aluminium, magnesium, nickel, cobalt, tin, zinc,antimony, silver, palladium, platina, &c., by mixing with our bathssalts or oxides of the metals we wish to alloy.- The baths being the oneacid, the others alkaline, we can exactly choose the mixture of saltsorof oxides which suit the best for the deposition of the alloys that wewish to obtain. We obtain likewise alloys'in employing, in our baths ofchromium, soluble anodes, as ferro-chrome,

nickel, iron, aluminium, zinc, copper, silver,

820. By taking baths of copper, of zinc, of iron, 'of aluminium, nickel,lead, tin, silver, gold,'&c., and in adding a certain quantity of one ofthe baths of chromium, that we have just indicated, we obtain depositsof copper, of zinc, of iron, aluminium, nickel, &c., which are" found tobe considerably improved by the presence of a certain quantity ofchromium which is deposited at the same time as the principal metal.Finallywe obtain alloys by chromium is 'depositing alternatelysuperposedlayers of chrome andof the metal that we wish to alloy, andmelting the whole.

baths is obtained which give depositions of Thirteenth. We workgenerally at the ordi nary temperature. However, we find t oftenadvantageous to beat our baths; which gives 'us more rapid and moreabundant depositions. In certain cases, even,we heat our baths toaqueous fusion and the igneous fusion of the salts that we employ. Thisis in effect how we work in certain cases. We take for exampleten tofifteen grams of bi-sul phate of potash, one hundred grams ofchromealum, and one hundred grams of water. We heat it tothe dissolutionof the salts; and we pass through it the electric current. The

negative pole. We maintain the baths by means of chrome-alum alone, orby means of a concentrated solution of chrome-alum and ofalkalinebisulphate. The bath is thus constantly renewed, and can consequentlylast' indefinitely. One can, mpreover, suppress water in the formationof the bath, and prepare the bath by heating, immediately, the mixtureof the salts to their fusion. .Weadd sometimes to these fused bathsasuitable salt of an alkaline earth metal.

Fourteenthfllhe fusion of chromium demands a very high temperature, andwe therefore employ, generally the electric current to eflfectthisfusion. Often to efiect this fusion instead of using electrodes ofpure carbon, we employ electrodes composed of carbon, oxide of chromium,of chrome-salts, or of flour of chrome, the whole previouslyagglomerated with a solventv (borax, phosphate lime, fluoride, the.) anda reducer (zinc, magnesium, aluminium, &c.)-so that we effect at thesame time the reduction and the fusion of the metal.

We may put into the composition of these electrodes foreign metals,copper, aluminium, zinc, nickel, silver, &c., or oxides of these metalsin order to obtain immediately the alloys of chrome and of these othermetals. Finally, we find it advantageous to introduce in the cruciblewhere we effect this fusion, inert gases or reducing gases, such ashydrogen, carbureted gases, gases containing the dust of zinc, ofaluminium, &c.; and we introduce these gases by the help of a tuyere, orsimply by the .interior itself of the'electrodes which in this case arehollow.

We would observe in" conclusion that, as we are well aware, Bunsen in1854 experimented with. protoohloride of chromium to obtain byelectrolysis infinitesimal particles of metallicv chromium. Theprotochloride of chromium (OrCl) is an extremely rare and expensivecompound costing now about one hundred. and fifty dollars per kilo, andmoreover very deposited immediately at the I too unstable, decomposinginstantly upon exposble e 8e. Theiprotoehloride has and could notbeusedsaye for'alaboratory experiment, and isessentially difierent 1nehar'scter and in results i'mm eliromic. acidor the-equivalents thereofemployed m our p I It has also been proposed to separate metals(chromium among others) from each other by transforming the metals intodouble oxalates and usingeolua tions of these in electrolytic baths.This method of analysis isof no value for and can- ..not be adaptedtofche extraction of chromium f posited at the negatii'e electrode is overyr impure and commercially worth less, being very differentfrom thepure-chic, A mini obtained by our process;

: of organic acids,

by electrolysis, because first, the metal debadqualit-y,

and second, as well as all compounds are too costly who usedoommercrally: 'We disclaim compounds formed r becanse'the oxaiates;

with organic acids. It has also beenfpro':

iumoh the surface-of posed to deposit chrom metallic objects flioma'bath of chromium dissolved in-a. doublechloride of sod-a and am in.this mannerand to plate othermetals m'enisi It is impossible to-dissolvechromium .theremth. Though this method was proposedin-1852, it iswellkneiyn: that'no arti eles electroplated rith-ehromium were ever will? 1P 9 'ried into practice.

1; The process herein described of produc= need until our presentinvention ,vlvas cer- 3'0 Wecleim as our invedxtiun'or discoveryingelectrolytip'deposits of metallic chromium,

by. passinr'an electric, current throu electrolytic. 'bath essentially01a soluble chromi'c compound, such as chromic acid, in aqueous solutionas set forth.

'2. The process herein described of producing metallic chromium, bypassi ng an electric current through a. bath containing'achnomiccompound, as specified, in aqueous solution, i

and a salt of an alkali fr alkali earth metal. 3. The described'processof obtaining elec' trolytic deposits of, chromium by forming a bath of asalt of compound of chromium,

'such as hereinbefore specified, and -a salt'o'l."

amalkali eartbmetal, heating the bath, an" I passing 1m electric currentthrough the mm .4,

substantially-as described.

Rom. M, Rodin;

Joshrrr loim'xmm 5e Intestimeny whereof We have signed'this

